Self-adjusting tappet



Feb 20, 1951 H. J. KNAGGS SELF-ADJUSTING TAPPET Filed April 20, 1945 INVENTOR. HA HOLD IKNAGfiS A TTOENEYS Patented Feb. 20, 1951 SELF-ADJUSTING TAPPET Harold J. Knaggs, Cleveland, Ohio, 'assignor to The Weatherhead CompanmCleveland, Ohio, a

corporation of Ohio Application April 20, 1945, Serial No, 589,308

4 Claims.

1 My invention relates to tappets and concerns particularly valve tappets for gas engines.

One of the objects of my invention is to provide a self-adjusting valve tappet.

The principal object of the invention is to compensate for variations in length of valve stems, valve rods or other operating rods for communicating reciprocating motion.

It is an object of the invention to overcome lost motion in internal combustion engines and to from the reservoir to the cylinder. An inertia operated check valve is provided in said opening for enabling the fluid to be transferred from the reservoir to the cylinder but opposing egress of the fluid from the cylinder into the reservoir in order to maintain tappet length during the pressure stroke of a cam operating a valve stem avoid variations of period and timing of valve opening as well as to avoid noise and wear of loose parts.

Another object is to compensate for the effect of variations in temperature on length of the valve rod and to avoid undue loss of efficiency of an internal combustion engine when the engine is still cool.

More specifically, an object is to provide for close adjustment of tappets while the engine is cool as well as when heating up.

A further object is to provide self-elongation and contraction of a tappet without external connections or controls.

Still another object is to provide reliable self-' contained hydraulic compensation for tappets in which paths for uncontrolled leakage of hydraulic fluid are eliminated.

A further object is to provide hydraulic'compensation for a tappet in which passage of hydrauic fluid from one part to another of the tappet is limited to predetermined -means for metering the flow.

An obect of my invention is the employment of inertia for opening and closing a valve.

Another object is to provide an arrangement for controlling fluid flow in a hydraulic tappet by the inertia effect of tappet movement.

Other and further objects, features, and advantages of the invention will become apparent as the description proceeds.

In carrying out my invention in a preferred form thereof, I employ an extensible and contractible tappet as a valve-lifter for an internal combustion engine in order to maintain minimum clearances of the engine valve.

The tappet in a preferred form of my invention comprises relatively movable parts, one of which is a hollow cylinder and the other a piston adapted to move within the cylinder and having a reservoir therein. The reservoir and cylinder are filled with a suitable hydraulic fluid such as oil, and the end of the piston toward the cylinder has a transverse inner wall with an opening therein through which fluid may be transferred through the tappet. Preferably, a ball check valve or a poppet check valve is employed.

A better understanding of the invention will be afforded by the following detailed description, considered in conjunction with the accompanying drawing, and the scope of the invention will be set forth in the claims appended hereto.

In the drawing:

Fig. 1 is a fragmentary sectional view of an internal combustion engine represented ascut by a p'ane passing through a push rod axis, and empoying an extensible tappet for automatic compensation of tappet clearance in accordance with my invention.

Fig. 2 is a fragmentary view showing in greater detail a portion of the apparatus in Fig. 1.

Fig. 3 is a longitudinal sectional view of an extensible self-compensating tappet employing a cylindrical poppet type of check valve.

Fig. 4 is a cross-sectional view of the apparatus of Fig. 3 represented as cut by a plane 44.

Fig. 5 is an enlarged fragmentary view of the bushing shown in Fig. 3 showing the leakage oove.

Like reference characters are utilized throughout the drawing to designate like parts.

Referring to Fig.v 1 the arrangement shown therein by way of illustration comprises a portion of a casing H for an internal combustion engine, such as a gasoline engine'for example, having a conventional poppet valve l2 controlled by valve stem l3 or controlled by a valve rod represented by the rod l3, slidable in a suitable guide or bushing I4. A valve spring I5 is provided for normally closing the valve It by moving the stem I3'in the downward direction. A tappet I 6 is provided for transferring the action of a valveoperating cam I! to the valve rod l3. As in conventional constructions, the tappet I6 has a hardened portion I 8 adapted to ride on the cam 23, takes the form of a hollow piston. A suitable, relatively incompressible, hydraulic fluid such as oil, for example, is provided for filling the cylinder 22 and a reservoir 25 is formed in the piston 23 for supplying oil to the cylinder 22 to extend the tappet length.

The cylinder 22 is closed at the lower or outer end and the piston 23 is provided with an inner transverse wall 26. For closing the piston. 23 above the inner transverse Wall 26, suitable means such as a plunger 21 may be provided.

There are means permitting restricted passage of the hydraulic fluid or oil between the reservoir 25 and the cylinder 22. For quick return of oil to the cylinder without leakage back into the reservoir 25, a suitable check-valve 28 is preferably provided in the transverse wall 26. In the arrangement of Fig. 1 the check-valve 28 is shown as being of the free-floating ball type.

To facilitate manufacturing and assembling operations, a screw-cap 29, the top of which forms the hardened top surface I9, may be provided at the upper end of the hollow piston 23 to form the top of the tappet I6. Suitable means are provided for sealing the plunger 21 in the piston 23 such as an O-ring 3| composed of re silient material such as rubber or synthetic composition, fitted in an annular groove 32 around the plunger 21 of greater cross section than the sealing ring 3|. In non-flexed or uncompressed condition resilient ring 3| has a diameter greater than the depth of the groove 32.

A similar seal is formed between the piston 23 and the cylinder 22 which may take the form of an O-ring 34 in an annular groove 35 around the portion of the piston 22 at which the transverse wall 26 is located.

Suitable means are provided for resiliently expelling or tending to expel hydraulic fluid from the reservoir 25 into the cylinder 22. This may be accomplished by means of the plunger 21. For forcing the plunger 21 downward upon the top surface of the body of oil in the reservoir 25, suitable means are provided such as a compression spring 33 between the screw-cap 29 and the plunger 21. The spring 33 is preferably weaker than the valve spring I5.

I'he check-valve 28 is of the ball and seat type and comprises a ball 36 with an upper seat 31 and a lower seat 38. The upper seat 31 takes the form of a shoulder in the opening 30 through the transverse piston wall 26. Preferably, the opening 39 is narrowed at the upper end to form a small orifice 39. The lower ball seat 38 is produced by threading a bushing 4| into the opening 30, the lower portion of which is internally threaded to receive the bushing 4|. The upper edge of the bushing 4| forms the lower ball seat 38.

In order that the oil or hydraulic fluid may pass readily in either direction, when the ball 36 is resting upon the lower seat 38 as well as when it is slightly raised, a groove 42 is preferably formed in the edge of the bushing 4 I.

The surface of the cam I1 may be divided into three distinctive portions, namely the portion between the points 43 and 44 during which the cam is rising and lifting the cam follower I8, the portion between the points 44 and 45 during which the cam surface is falling and allowing the cam follower I8 to fall, and the portion between the points 43 and 45 representing the base circle upon which the cam follower surface I8 rests or dwells without motion in either direction. During the time that the portion of the cam surface between the points 43 and 44 is contacting the cam follower I8 forcing the cylinder 22 upward against the pressure of the spring I5, pressure is applied to the body of fluid 24 causing the fluid to rise through the opening 30 and to lift the ball 36 against the upper seat 31, thus closing the check valve 28. This action prevents flow of oil from the cylinder 22 into the reservoir 25 and thus prevents contraction of the tappet I6.

A certain amount of fluid, however, is permitted to escape through the orifice 39 into the reservoir 25 during the time required for the ball 36 to rise against the seat 31. This slight amount of fluid has an imperceptible efiect upon the length of the tappet, but with successive strokes permits the tappet length to adjust itself, when required, to permit the valve I2 to close fully when the cam follower I8 is resting upon the base circle of the cam I1. This condition may arise, for example, in case the engine is re-started after it has cooled off and the changes in temperature have affected the valve clearances.

However, as the engine warms up increasing the clearances between the cam I1 and the pushrod I3, most efilcient operation of the engine requires the reduction of the clearance to zero by the extension of the tappet I6. This is accomplished by the pressur of the plunger 21 downward upon the upper surface of the fluid in the reservoir 25. When the cam I1 i no longer on the pressure stroke, the pressure on the hydraulic fluid is relieved, enabling th spring 33 to press the plunger 21 downward and expel oil from the reservoir 25 through the orifice 39 and the opening 30. In the event that this pressure should be insuflicient to break the seal between the ball 36 and the upper seat 31, the inertia of the ball 36 will break the seal when the tappet is abruptly brought to rest at the end of the down stroke of the cam, when the cam follower I8 comes to rest upon the base circle between the points 43 and 45 of the cam I1. Fluid then passes from the reservoir 25 through the orifice 39 around the ball 36 and through the remainder of the opening 30 into the cylinder 24, extending the tappet in length until all clearance is closed between the upper end I9 of the tappet and the lower end 2| of the push rod, and valve I2 then being seated. Since the spring 33 is weaker than the valve spring I5, there is no tendency for the action of the plunger 21 to lift the valve I2 from its seat. However, the ball 36 may drop to its seat 38 and rest directly upon it while the oil is flowing from the reservoir 25. No interference is caused with the transfer of oil to the cylinder 22 owing to the passage permitted by the groove 42. The force of the spring 33 is, however, preferably suflicient to overcome friction of the O-rings 3| and 34.

A greater degree of inertia effect for opening the check valve 28 may be obtained by utilizing a heavier valve closing member such as a poppet 46, for example, as illustrated in Fig. 3. The poppet 46 preferably has a cylindrical main outer surface with frusto-conical ends 41 and 48 adapted to engage upper and lower valve seats 31 and 38' respectively. It will be understood that a cylindrical recess 49 is provided of suflicient length in the opening 30 for receiving the poppet 46. The use of substantially frusto-conical seat engaging surfaces 41 and 48 has a certain advantage over the use of spherical surfaces, as in the case of a ball check valve, in that it reduces the cost of machining and finishing operations on the seats 31' and 38. As seen in Fig. 5, in the arrangement of Fig. 3, a groove 42' such as the groove 42 of Figs. 1 and 2 is preferably employed for the same purpose as in the arrangement of Fi s. 1 and 2.

To avoid possibilities of critically loading the reservoir 25 and the cylinder 22 with oil or other hydraulic fluid, a recess or drain hole is preferably provided. The drain hole 5| is drilled into the side of the hollow piston 23 at the point determining the desired upper limit of the body of oil to be contained in the cylinder 22 and the reservoir 25. If any excess oil should be placed in the reservoir 25 during assembly, this excess leaks out through the hole 5|, but thereupon the plunger 21 is permitted to move downward in the piston 23 below the drain hole 5| so as to prevent the leakage of any further fluid.

Assembly of the apparatus is preferably carried out in the following manner. With the piston 23 separated from the cylinder 22 and inverted, and with the cap 29 removed, the ball 33 or the poppet 46 is dropped in place in the opening 30 whereupon the bushing 4| is threaded into position retaining the ball 36 or the poppet 46. The cylinder 22 is then placed with the closed end downward and partly filled with oil whereupon the piston 23 is inserted in the cylinder 22 and the oil is allowed to rise through the opening 30, until all of the air is expelled from under the check valve, and the check valve is seated by oil pressure. The piston is pressed downward slowly enough so that the entrapped air escapes through the groove 42 and does not lift the ball 36 on the poppet, whereupon additional oil is poured into the piston 23, the upper end which is still open. After a quantity of oil has been poured therein to insure covering the portion of the opening 30 around the upper seat 31 and provide a body of oil above the transverse wall 26 substantially up to the drainage hole 5|, the plunger 21 is inserted. The spring 33 is then inserted and compressed sufllclently to enable the cap 29 to be inserted into the upper end of the piston 23 to be threaded in place, thus leaving the spring 33 into comcertain' embodiments of my invention and certain methods of operation embraced therein for p the purpose of explaining its principle of operapressed condition and urging the plunger 21 downward against the oil surface in the reservoir 25. Any excess oil or entrapped air under the plunger 21 is expelled through the drain hole II.

In connection with Figs. 1 and 2, I have shown an O-ring arrangement including an O-ring 34 composed of compressible material for sealing the piston 23 in the cylinder 22. However, my invention is not limited to the specific arrangement illustrated in Figs. 1 and 2 as other sealing means may be employed. For example, as illustrated in Fig. 3, the lower end of the piston 23 may be so formed and a bushing 4| of such dimensions may be employed that the bushing 4| extends below the lower end of the piston 23 and a gasket of suitable resilent material such as rubber or synthetic composition 52 may be cemented around the outer surface of the bushing 4| at the lower end thereof. The surfaces of the gasket 52 are pressed against the lower edge of the piston 23 and against the internal surface of the cylinder 22 when the bushing 4| is threaded into position. I As in the arrangement of Figs. 1 and 2, the arrangement of Fig. 3 serves to compensate automatically for conditions such as the changes in temperature which would tend to change valve clearances, and the tappet thus continually hunts for the proper length which reduces the clearance to zero.

" I have herein shown and particularly described tion and showing its application, but it will be obvious to those skilled in the art that many modifications and variations are possible and I aim, therefore, to cover all such modifications andvariations as fall within the scope of my invention which is defined in the appended claims.

What is claimed is:

1. A tappet comprising a cylinder member, a piston member telescoped with said cylinder member, fluid sealing means between said cylinder and piston members, said members cooperating to form a hydraulic pressure chamber, a hydraulic reservoir chamber formed in one of said members, said pressure chamber and reservoir chamber having a common wall portion integral with one of said members, a liquid transfer opening formed in said common wall portion, a valve seat formed in said common wall in the transfer opening, said seat facing said pressure chamber, a check valve member in said opening, and means loosely retaining said check valve in said opening with the valve spaced from said seat and away from said reservoir chamber when engaging said retaining means, hydraulic liquid within said pressure chamber and saidreservoir chamber, resilient means in said reservoir chamber for causing transfer of liquid through said transfer opening from the reservoir chamber to the pressure chamber while said valve is away from its seat to thereby allow relative movement of said members in order to increase the tappet length, loading of said tappet on the lift stroke causing a small amount of fluid to pass from the pressure chamber and sweep past said check valve to the reservoir thereby slightly shortening said tappet, said check valve being carried against said seat by the sweep of said fluid after which pressure in said pressure chamber holds the valve against said seat, said fluid sealing means insuring that all fluid transfer bztween said chambers occurs through said opening, said check valve blocking fluid transfer from the chamber to the reservoir when engaging said seat.

2. A tappet comprising a cylinder member, a piston member telescoped with said cylinder member, fluid sealing means between said cylinder and piston members, said members eooperating to form a hydraulic pressure chamber, a by draulic reservoir chamber formed in one of said members, said pressure chamber and reservoir chamber having a common wall portion integral with one of said members, a liquid transfer opening formed in said common wall portion, a valve seat formed in said common wall in the transfer opening, said seat facing said pressure chamber, a check valve member in said opening, and means loosely retaining said check valve in said opening with the valve spaced from said seat and away from said reservoir chamber when engaging said retaining means, hydraulic liquid within said pressure chamber and partially filling said reservoir chamber, resilient means in said reservoir chamber for causing transfer of liquid through said transfer opening from the reservoir chamber to the pressure chamber while said valve is away from its seat to thereby allow relative movement of said members in order to increase the tappet length, loading of said tappet on the lift stroke causing a small amount of fluid to pass from the pressure chamber and sweep past said check valve to the reservoir thereby slightly shortening said tappet, said check valve being carried against said seat by the sweep of said fluid after which pressure in said pressure chamber holds the valve against said seat, said fluid sealing means insuring that all fluid transfer between said chambers occurs through said opening, the inertia of said check valve relative to the size of said opening being such that said check valve breaks loose from its seat, on the down stroke, said check valve blocking fluid transfer from the chamber to the reservoir when engaging said seat.

3. A tappet comprising a cylinder member, a piston member telescoped with said cylinder member, fluid sealing means between said cylinder and piston members, said members cooperating to form a hydraulic pressure chamber, a hydraulic reservoir chamber formed in one of said members, said pressure chamber and reservoir chamber having a common wall portion integral with one of said members, a liquid transfer opening formed in said common wall portion, a valve seat formed in said common wall in the transfer opening, said seat facing said pressure chamber, a ball check valve member in said opening, and means loosely retaining said check valve in said opening with the valve spaced from said seat and away from said reservoir chamber when engaging said retaining means, hydraulic liquid within said pressure chamber and said reservoir chamber, resilient means in said reservoir chamber for causing transfer of liquid through said transfer opening from the reservoir chamber to the pressure chamber while said valve is away from its seat to thereby allow relative movement of said members in order to increase the tappet length, loading of said tappet on the lift stroke causing a small amount of fluid to pass from the pressure chamber and sweep past said check valve to the reservoir thereby slightly shortening said tappet, said check valve being carried against said seat by the sweep of said fluid after which pressure in said pressure chamber holds the valve against said seat, said fluid sealing means insuring that all fluid transfer between said chambers occurs through said opening, the inertia of said ball check valve relative to the size of said opening being such that said ball breaks loose from its seat on the down stroke, said ball check valve blocking fluid transfer from the chamber to the reservoir when engaging said seat.

4. A tappet comprising a cylinder member, a piston member telescoped with said cylinder member, fluid sealing means between said cylinder and piston members, said members cooperating to form a hydraulic pressure chamber, a hydraulic reservoir chamber formed in one of said members, said pressure chamber and reservoir chamber having a common wall portion integral with one of said members, a liquid transfer opening formed in said common wall portion, a valve seat formed in said common wall in the transfer opening, said seat facing said pressure chamber, a poppet check valve member in said opening, and means loosely retaining said check valve in said opening with the poppet spaced from said seat and away from said reservoir chamber when engaging said retaining means, hydraulic liquid within said pressure chamber and said reservoir chamber, resilient means in said reservoir chamber for causing transfer of liquid through said transfer opening from the reservoir chamber to the pressure chamber while said poppet is away from its seat to thereby allow relative movement of said members in order to increase the tappet length, loading of said tappet on the lift stroke causing a small amount of fluid to pass from the pressure chamber and sweep past said poppet to the reservoir thereby slightly shortening said tappet, said check valve being carried against said seat by the sweep of said fluid after which pressure in said pressure chamber holds the valve against said seat, said fluid sealing means insuring that all fluid transfer between said chambers occurs through said opening, the inertia of said poppet check valve relative to the size of said opening being such that said poppet breaks loose from its seat on the down stroke, said poppet blocking fluid transfer from the chamber to thereservoir when engaging said seat.

HAROLD J. KNAGGS.

REFERENCES CITED The following references are of record in the file of this patent:

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